There are two basic ways of controlling the quantity of ink being transferred to an ink receiving roller from an ink trough. One such way is the application of a doctor blade against the ink receiving roller, to strip off ink being picked up thereby and leave only a film thereon, the thickness of which is controlled by the setting of the doctor blade against the roller. Zone screws can be used to vary the quantity of ink being transferred in axially adjacent zones. Another way is to apply ink in rings or strips, in which the thickness of the ink film being applied is always the same, and using resilient, axially shiftable metering tongues, engaging the roller, and changing the amount of ink being transferred to the roller.
German Pat. No. 26 48 098 describes an arrangement of the first type, in which metering elements are used, resiliently engaged against the ink receiving roller. The metering elements, which can be separately controlled by zoning adjustment screws, permit metering of the ink; use of separate resilient spring-like engagement has the advantage that the thickness of ink being transferred at any one zone will be the same, regardless of centricity errors which may occur in the roller. Such metering arrangements have a disadvantage, however: If the quantity of ink required is very small, so that at least some of the zones of ink transfer have only very thin films of ink applied thereto, the metering arrangement is particularly subject to contamination with respect to fine particles, dirt, and the like, which may be transferred to the ink application roller from the ink trough. Solids, and particularly solid particles, grains, and other elements may jam between the resilient application blade and the ink receiving roller, and then, in operation, firmly adhere thereto. The quantity of ink being transferred thus becomes uncontrollable, and the uniformity, particularly of thin ink layers, is not retained. A further disadvantage is this: The respective metering elements are engaged with the rollers in an almost tangential engagement. Due to the high hydrodynamic forces, the spring force must be high, which is damaging both to the doctor blade elements as well as to the ink receiving roller if the doctor blade actually engages the surface thereof. The second type of ink transfer arrangement--see German Democratic Republic Pat. No. 120,833--transfers ink in ring-shaped strips throughout the width of the ink receiving roller, and the quantity of ink being transferred is determined by the width of the raspective strips of ink, in the respective ink zones. The thickness of these ring-shaped strips will always be the same. The ink receiving roller is then engaged with rollers of a roller train, some of which are axially oscillating, to provide for milling of the ink film on the respective rollers of the roller train, and thus render essentially uniform the ink film on the rollers of the inker roller train. The milling rollers, thus, distribute the ink so that a film of ink in zones of varying thickness will be obtained eventually by the rollers of the roller train. The metering principle of this type eliminates the danger of collection of solid particles and the like which arises in the inker of the first type described, since, even if the ink requirement is low, a sufficient distance between the metering range of any one ink zone and the ink receiving roller can be maintained. The required width of the ink film, in accordance with this disclosure, is determined by adjacently located longitudinally shiftable metering tongues which include wedge-shaped notches, thereby forming adjacently located support regions and metering regions. The metering tongues, which are elastic and tangentially engage the ink receiving rollers with their support regions, can be shifted in axial direction only with comparatively high force due to the hydrodynamic pressure arising in operation.